Polymers having reactive terminal silyl groups or compositions comprising such polymers can be hydrolyzed and condensed in the presence of water and organometal catalysts. Suitable known catalysts for curable compositions include organometallic compounds employing metals such as Sn, Ti, Zn or Ca. Organotin compounds such as, for example, dibutyltin dilaurate (DBTDL) are widely used as condensation cure catalysts to accelerate the moisture assisted curing of a number of different polyorganosiloxanes and non-silicone polymers having reactive terminal silyl groups such as room temperature vulcanizing (RTV) formulations including RTV-1 and RTV-2 formulations. Environmental regulatory agencies and directives, however, have increased or are expected to increase restrictions on the use of organotin compounds in formulated products. For example, while formulations with greater than 0.5 wt. % dibutyltin presently require labeling as toxic with reproductive 1B classification, dibutyltin-containing formulations are proposed to be completely phased out in consumer applications during next 4-6 years.
Alternative organotin compounds such as dioctyltin compounds and dimethyltin compounds can only be considered as a short-term remedial plan, as these organotin compounds may also be regulated in the future. It would be beneficial to identify non-Sn metal catalysts that accelerate the condensation curing of moisture curable silicones and non-silicones. Desirably, substitutes for organotin catalysts should exhibit properties similar to organotin compounds in terms of curing, storage, and appearance. Non-tin catalysts would also desirably initiate the condensation reaction of the selected polymers and complete this reaction upon the surface and may be in the bulk in a desired time schedule. There are therefore many proposals for the replacement of organometallic tin compounds by other organometallic compounds. These compounds comprise metals such as Ca, Ce, Bi, Fe, Mo, Mn, Pb, Ti, V, Zn and Y. All of these metals have specific advantages and disadvantages in view of replacing tin compounds perfectly. Therefore, there is still a need to overcome some of the weaknesses of possible metal compounds as suitable catalyst for condensation cure reaction and behavior of uncured and cured compositions in particular to maintain the ability to adhere onto the surface of several substrates.
The use of manganese (II) complexes as catalysts in silicone compositions has been described. For example, U.S. Pat. No. 7,115,695 describes the use of manganese (II)-carboxylate as a catalyst for cross-linking silyl-capped organic polymers including additional promoters. U.S. Pub. No. 2008/0242825 mentions the use of a manganese catalyst in a process for endcapping polyethers with alkoxysilyl groups. U.S. Pat. No. 5,304,621 discloses the use of a manganese (II)-carboxylate compound as a condensation catalyst for polyorganosiloxanes having additional organyloxy and hydrogen groups. Other than these general teachings that group manganese complexes together, there does not appear to be any teachings that differentiate the catalytic activity exhibited by different manganese complexes.
WO 2009/106719 A1 and WO 2009/106722 A1 disclose among others, e.g., manganese (III) pentanedionate in a generic list including Bi, Ce, Fe, Mo, Yb compounds and propose the use of these complexes or complexes having additional anions as polycondensation catalysts in polyorganosiloxane compositions, whereby the use and reduction to practice is only disclosed for selected Bi, Ce, Fe, Mo, Sn complexes. The disclosed polyorganosiloxane compositions comprise either only a SiOH terminated combined with ethylsilicate as a crosslinker or a VTMO-terminated polymer, which has been cured with Bi, Ce, Fe, Mo, Sn catalysts in the presence of water or moisture. Another problem necessary to be solved in the replacement of organo-tin compounds is the property of the reactive composition to maintain its ability to cure after storage in a sealed cartridge, when exposed to humidity or ambient air.